Johnson & Johnson announced on Wednesday that it had finalised a deal to buy Momenta Pharmaceuticals Inc for about $6.5 billion in cash, with the aim of growing its portfolio of autoimmune disease treatments.

The main prize of the deal was nipocalimab, Momenta’s experimental therapy drug that is currently being tested against myasthenia gravis – a neuromuscular disease that weakens muscles – and other diseases that cause the immunes system to attack the body. Following the deal, J&J’s Janssen Pharmaceutical Companies will gain access to the treatment.

“Janssen will have the potential to introduce multiple launches, many as first-in-class indications with potential for significant peak year sales, some of which could exceed $1 billion,” J&J said in a statement.

The merger also allows J&J’s Janssen division to reach more patients by enhancing its ability to treat autoimmune diseases and improve health outcomes.

Jennifer Taubert, J&J’s Executive Vice President and Worldwide Chairman of Pharmaceuticals, also lauded the deal. “This acquisition broadens Janssen’s leadership in autoimmune diseases and provides us with a major catalyst for sustained growth,” she said.

“We’re excited by the opportunity to further advance patient care by combining Johnson & Johnson’s world-class R&D, commercial and supply chain capabilities with Momenta’s talented people, pipeline and deep expertise in this important area.”

J&J is also one of the medical companies working to develop an effective COVID-19 vaccine, and has recently signed deals with the US and UK for future doses.